Various attempts have been made to provide a single tool for removing fastener components having many sizes and shapes. Primarily, those attempts have involved two distinct design approaches. One approach to designing such a tool has been to utilize a socket housing forming a longitudinal chamber holding a set of symmetrically-shaped, concentrically-nested, longitudinally telescoping sockets. Patents disclosing devices of this general type include Greiner, U.S. Pat. No. 1,896,949, issued Feb. 7, 1933, Pearson, U.S. Pat. No. 1,997,948, issued Apr. 16, 1935, Svenson, U.S. Pat. No. 2,875,660, issued Mar. 3, 1959, Haber, U.S. Pat. No. 2,938,417, issued May 31, 1960, Rogers, U.S. Pat. No. 3,127,797, issued Apr. 7, 1964, Mahall, U.S. Pat. No. 3,250,158, issued May 10, 1966, Mahall, U.S. Pat. No. 3,262,338, issued Jul. 26, 1966, Svenson, U.S. Pat. No. 3,285,106, issued Nov. 15, 1966, Lynn, U.S. Pat. No. 3,298,261, issued Jan. 17, 1967, Nicastro, U.S. Pat. No. 4,489,628, issued Dec. 25, 1984, Hurst, U.S. Pat. No. 4,528,875, issued Jul. 16, 1985, Kim, U.S. Pat. No. 5,074,174, issued Dec. 24, 1991, Nogues, U.S. Pat. No. 5,157,995, issued Oct. 27, 1992, and Mathers, U.S. Pat. No. 5,163,344, issued Nov. 17, 1992.
Another approach to designing a universal tool has been to utilize a socket housing forming a longitudinal chamber having a first end and holding a bundle of pins, bars or rods of uniform shape and size with the first ends of such pins nominally proximal to the first end of the chamber. When a fastener component contacts the ends of the pins, the contacted pins are displaced away from the first end of the chamber. The pins that are not contacted by the fastener component remain in their nominal positions, surrounding the component and providing surfaces against which the fastener component can be gripped for turning. The designs following this general approach utilize cross sections that are square, circular, octagonal and triangular in shape. In some of these designs, the pins are thin enough as to engage the recessed slots of Phillips or slotted screws. Patents disclosing devices of this general type include Wiedmann, German Patent No. 315,926, issued Apr. 26, 1918, Popper, U.S. Pat. No. 3,251,251, issued May 17, 1966, Locke, U.S. Pat. No. 3,349,655, issued Oct. 31, 1967, Denney, U.S. Pat. No. 3,698,267, issued Oct. 17, 1972, Pasbrig, U.S. Pat. No. 3,858,468, issued Jan. 7, 1975, and Zayat, U.S. Pat. No. 4,887,498, issued Dec. 19, 1989.
A typical universal tool utilizing this design is described in Zayat, which discloses a bundle of over four hundred individual pins longitudinally suspended within a chamber by a plurality of side-by-side rails, and biased to a nominal position by individual springs mounted on rods connecting the pins to the rails. The pins are shown to be of a uniform circular or square cross-section. The Zayat design relies on its many relatively small pins to provide a snug fit around the component head. Due to the pins' small cross sectional areas, each pin relies on the support of the surrounding pins and the housing to prevent the pin's disfigurement or fracture. Because of the small cross-sectional area of the many pins, the '498 tool accommodates a great many shapes and sizes of components, including Phillips and slotted-screws.
With respect to the telescoping socket designs, although they are inherently structurally strong, one of their disadvantages is that relatively few sockets can be nested in a single tool before the tool becomes too large or unwieldy to use, such that the variety of fastener shapes and sizes with which the sockets are compatible is extremely limited. Additionally, any fastener component to be turned must be centered with respect to the first end of the chamber of the tool, and if a socket size compatible with that component is not available, the component cannot be turned.
Similarly, designs utilizing bundles of uniform pins or rods suffer from a number of disadvantages. For example, the uniform square and circular pin shapes suggested by Zayat, and the other similar shapes suggested by other prior art references, are not well adapted to provide the structural stability necessary to withstand the application of large amounts of torque. Additionally, the small cross-sectional area-to-length ratios of the pins renders the pins susceptible to disfigurement or fracture during use of the wrench, especially when extracting a fastener component having a head with a large cross-sectional area compared to the cross-sectional area of the housing chamber. In such a situation, the component approaches the outer perimeter of the chamber and relatively few of the pins can be used to transmit torque to the fastener head, thus decreasing their structural support and making structural failure more likely. Another disadvantage is that, similar to the complicated suspension and pin biasing systems disclosed in Zayat, the several pin-bundle references disclose pin suspension and biasing systems that are complicated, ineffective, difficult to assemble, or expensive to manufacture.